Month: July 2016

3-D rendering based on a μCT scan (A) alongside an SEM micrograph (B; 1000x magnification) of a biopolymer composite stained with 1.5 wt.% iodine and fixed with HMDS.

“μCT scanning of low density porous polymer scaffolds leads to insufficient imaging ability due to poor contrast. In order to enhance their X-ray absorption, one might trial several approaches using contrast agents. This methods paper is aimed at guiding scientists in applying the most appropriate contrast enhancement method for CT imaging of such materials, by reporting both the positive and the negative results. Iodine staining coupled with chemical drying was the most efficient approach, allowing for contrast enhancement, morphology preservation, and high resolution all at once.”

The ability to visualize hard tissues (e.g., bone, dentine, enamel) rapidly in three dimensions using X-ray computed tomography (CT) has been one of the most important advancements in the field of vertebrate morphology in the last half-century. Until recently, however, comparably valuable advances in soft-tissue imaging have been difficult to realize fully due to the inherently low X-ray absorption of non-mineralized structures. Pioneering work in this area has demonstrated that Lugol’s iodine (I2KI) is a highly effective contrast agent for rapidly differentiating many types of soft tissues (e.g., epithelial, muscular, and neural structures) in micro computed tomography (μCT) images. Vertebrate morphologists have become a driving force in advancing this technique and utilizing the remarkable data generated from it to reconstruct phenotypes and functional anatomy in three and four dimensions.

Given the broad potential for iodine-enhanced CT imaging to become a major tool for soft-tissue reconstruction in vertebrate morphology, we will hold a symposium at the 2016 ICVM meeting to exhibit the wide range of taxa and questions that can be examined using these approaches. Through our symposium, Diffusible iodine-based contrast-enhanced computed tomography (diceCT) and related imaging techniques for research in evolutionary morphology, we will feature the newest and ongoing applications of contrast-enhanced three-dimensional (3-D) imaging already being undertaken by researchers within the International Society of Vertebrate Morphology. We further propose to hold a student-focused, combined poster session with the Hartstone-Rose and Marchi symposium on muscle functional morphology, to bridge the related techniques of our respective presenters. Our goal is to spur the further adoption of these methods by vertebrate morphologists. We will achieve this by (1) highlighting recent methodological advances in contrast-enhanced CT and μCT imaging, (2) demonstrating active research that integrates diceCT and related imaging techniques into toolkits addressing macroevolutionary questions, and (3) generating discussions of future directions and the long-term place for contrast-enhanced imaging in the study of extant vertebrates. We have assembled a diverse group of speakers who have enthusiastically agreed to participate in this symposium. They include well-established researchers, emerging early-career scientists, and graduate students in the fields of functional morphology, biomechanics, phenotypic integration, and vertebrate paleontology, whose academic contributions have already brought important insights to evolutionary biology. Demonstration of the high-level inferences that can be garnered with diceCT will spur collaborations among labs already exploring this powerful new tool with those who are considering how to apply it to their own research questions.